Manufacture of ethylene glycol



Nov. 26, 1929.

Filed ms. 2, 1928 Mal REY-

s m m m m www mwuum Patented Nov. 26,1929

4 UNITED STATES PATENT OFFICE KENNETH HERBERT SAUNDERS, F BL ACKLEY,MANCHESTER, AND HARRY WIGNALL, OF HUDDERSFIELD, ENGLAND, ASSIGNORS TOBRITISH DYESTUFFS CORPORATION LIMITED, 01? BLACKLE'Y, MANCHESTER,

ENGLAND MANUFACTUREOF ETHYLENE GLYCOL Application filed February 2',1928, Serial No. 251,459, and in Great Britain February 8, 1927.

In the usual methods of manufacturing ethylene glycol and its anhydride,ethylene oxide, the initial material isa crude weak solution of ethylenechlorohydrin made from 5 ethylene with the aid of chlorin and Water orHOCl. This solution is distilled to produce stronger purer liquiddistillates and these dist-illates are alkalized to produce ethyleneglycol or oxide as the case may be.

The operation is not a continuous one. The

object of the present invention is to make concentration andalkalization continuous, while it is a special feature of the presentprocess that loss of heat is avoided by omitting the 1 condensation ofthe vapour of the ethylenechlorohydrin incident to distillation.

According to this invention we may obtain the glycol either in the formof ethylene glycol itself, or in the form of its anhydride ethyleneoxide, as described hereafter.

By ethylene glycol in this specification is meant both the glycol assuch and in the form of its anhydride.

The mode of action is as follows:

At the bottom of a scrubber tower, lagged and filled .with suitablepacking, a steady stream of steam enters and ascends against adescending flow of crude weak chlorohydrinsolution. The amount of thissteam is adjusted so that it is exactly suificient to volatilize and tocarry upwards the ethylene chlorohydrin contained in the stream of crudesolution admitted at the top. It is important that the rate of the flowof the solution should be accurately controlled. The current or steamladen with ethylene chlorohydrin leaving the top of the packed tower,traverses a fractionating column-and passes away at the head thereof,carrying 95 per cent of the ethylene chlorohydrin originally containedin the crude solution. When the counter current tower is elficientlyworked the constitution of the vapours at the head of the fractionatingcolumn is such that, if condensed as a whole, a per cent aqueoussolution of ethylene chlorohydrin would be obtained, i. e. theconstitution approximates to that of the ethylene chlorohydrin constantboiling solution. The spent liquor and condensed steam flow away by thetrap at the bottom of the counter current scrubbing tower.

In the accompanying illustration we have shown diagrammatically a plantsuitable in the operation of the present invention, the showing beinggenerally in elevation with certain parts in vertical section. As so fardescribed, the output of the system is ethylene chlorohydrin vapors ofsuitable concentration. In the present invention, these vapors aresubmitted to alkalization without intermediate condensation to liquid.

The ethylene chlorohydrin vapour, together with any volatile impuritiescoming fromthe crude solution, passes down a well-lagged pipe A to thebottom of a second packed tower B (packing notshown), which it enters bybubbling through the hot liquid contained at the bottom. This liquid iskept hot either by external burners or other suitable means. The admixedethylene chlorohydrin vapours and steam ascending this tower meet adownflowingsolution of sodium carbonate, if the ethylene glycol as suchis to be obtained, or of caustic alkali it it is required in the form ofits anhydride, admitted in the correct proportion through the inlet tubeG. The The ethylene chlorohydrin is hydrolyzed to the glycol withconcomitant production of salt (N aCl) whilst steam, carbon dioxide andvolatile unhydrolyzable impurities pass away to a first condenser D; theethylene glycol dissolves in the salt solution and is carried downto,the bottom of the tower. Proper regulation of the supply of heat tothe bottom of the tower enables the glycol solution, which flows away bythe trap to the glycol recovery system (not shown), to be asconcentrated as desired up to the cr stallization point ofits salinecontents. T e glycol 9 solution flows from the trap direct to the dosalter or other standard concentration lant. The water and oilyimpurities, con ensed in D, are collected in a catch-pot E where theyform two layers. The oily portion is usually 95 heavier than waterbecause of the presence of chlorohydrin and underlies the aqueousportion of the condensate. The oil is drawn oil at the bottom and thewater overflows at the top into the gas-separator F. Carbon di- 1 oxidepasses away bythe pipe G, and water overflows to waste at the trap H.

When the glycol is obtained in the form of its anhydride by treating theascending vapors in B with a solution of caustic alka introduced at C,the gaseous ethylene'oxide .of the e usual.

(C H O) passing away at the tog tower is dried and collected in tmanner.

"What we claim and desire 'to secure by Letters Patent is z 1. In thecontinuous rod-notion of ethylene derivatives from cru e weak solutionsof ethylene chlorohydrin the recess which comprises steam distilling suea solution to produce hot concentrated ,vapors of the chloro-.

such hot vapors" in w of an alkaline soluhydrin and passingcountercurrent to a 0 tion. v

2. Inthe continuous derivatives from cru e'weak solutions of ethylenechlorohydrin the'process which com- 4 prises steam distillingsuch asolution to produce hot concentrated va ors of the chlorohydrin andpassing such ot vapors in countercurrent' toua flow of caustic alkali 1solution.

In testimony tures.

KENNETH HERBERT SAUNDERS.

HARRY WIGNALL- as I roduction of ethylene 3 whereof we afiix our signa-

